The present invention relates to an optical device used as an image panel allowed to be connected to the adjacent one without a gap put therebetween, and a method of manufacturing the optical device.
Recently, an electroluminescence device using an organic luminescent material (hereinafter, often called an xe2x80x9corganic EL (electroluminescence) devicexe2x80x9d, which emits natural light, having a high-speed responsiveness, and is not dependent on the viewing angle, has been extensively used as a flat electronic display.
FIG. 15 shows one example of a related art organic electroluminescence (EL) device 10A. The organic EL device 10A is of a double-hetero type in which an ITO (Indium Tin Oxide) transparent electrode 5, a hole transfer layer 4, a luminescent layer 3, an electron transfer layer 2, and a cathode (typically an aluminum electrode) 1 are sequentially formed on a transparent substrate (typically a glass substrate) 6 by a vacuum vapor-deposition method or the like.
When a DC voltage 7 is selectively applied between the transparent electrode 5 as an anode and the cathode (hereinafter, often called a metal electrode) 1, holes as carriers injected from the transparent electrode 5 migrate through the hole transfer layer 4 while electrons injected from the cathode 1 migrate through the electron transfer layer 2, to cause re-combination of the electrons and the holes, thereby emitting light 8 having a specific wavelength. Such light can be observed from the transparent substrate 6 side.
FIG. 16 shows another prior art example using an organic luminescent material, in which a hole transfer layer material or an electron transfer material serves as the luminescent material. Concretely, FIG. 16 shows an organic EL device 10B of a single-hetero type including an electron transfer layer 2 containing the luminescent material in place of omission of the luminescent layer 3 of the example shown in FIG. 15, whereby light 8 having a specific wavelength is emitted from the interface between the electron transfer layer 2 and a hole transfer layer 4.
FIGS. 17 to 19 show examples each having a basic configuration similar to that shown in each of FIGS. 15 and 16 and additionally including another element. In these figures, the electron transfer layer 2, the luminescent layer 3 (which is omitted in FIG. 16), and the hole transfer layer 4 shown in FIGS. 15 and 16 are collectively shown as an organic layer 9.
FIG. 17 shows the most basic example, in which a region where light emitted from an organic layer 9 is reflected from a metal electrode 1 becomes a luminescent region 36.
FIG. 18 shows the example in which a metal electrode 1 is formed in such a manner as to entirely cover an organic layer 9 and the peripheral edge of the organic layer 9 is insulated from the transparent electrode 5 by means of an insulating layer 32. In this example, since the insulating layer 32 is protruded in the peripheral edge portion of the organic layer 9, a luminescent region 36 is correspondingly narrower than that shown in FIG. 17; however, the deterioration of peripheral edge portion of the organic layer 9 can be prevented by the presence of the insulating layer 32.
FIG. 19 shows the example in which the stacked body on the transparent substrate 6 in the structure shown in FIG. 18 is covered with a protective layer 21. This example is effective to prevent the oxidation of the organic EL device (particularly, metal electrode) and hence to improve the durability of the organic EL device.
FIG. 20 shows an practical example of the above-described organic EL device. In this example, a stacked body of organic layers (a hole transfer layer 4, a luminescent layer 3 (which may be omitted), and an electron transfer layer 2) is disposed between stripes of cathodes 1 and stripes of anodes 5 which cross the stripes of the cathodes 1 in a matrix. Signal voltages are applied between the cathodes 1 and the anodes 5 in time series from a luminance signal circuit 33 and a control circuit 34 containing a shift register, to emit light at a number of crossing positions (pixels).
The organic EL device having the above configuration can be used not only as a display but also as an image reproducing apparatus. It should be noted that by arranging the above stripe patterns for each of red, green and blue, the organic EL device can be used as a full-color or multi-color type display or image reproducing apparatus.
As shown in FIG. 20, a driver circuit or the like has been connected to a flat luminescence device such as an organic EL device by drawing row electrodes and column electrodes up to the outer edge side of an image display region, and bonding FPCs (flexible print circuits) to the electrodes using an anisotropic conductive adhesive or the like.
Accordingly, when a plurality of organic EL devices are flatly connected to each other on a display as shown in FIG. 21, it becomes essential to put a specific distance D as a wiring space between adjacent ones of the organic EL devices.
Such a connection method, however, has the following problem. Since a plurality of the organic EL devices are connected to each other with gaps put therebetween, if the organic EL devices are used as image panels for a display, the image panels cannot be connected to each other without formation of relatively wide seams, thereby failing to clearly form one continuous image on the display. As a result, the image panels composed of the above organic EL devices cannot be used, particularly, for a tiling display in which the image panels are required to be arranged as closely-laid tiles.
To solve the above problem, the present inventor has proposed a method of forming a hard coat layer on the back side of an organic EL device, forming holes in the hard coat layer at electrode portions to expose electrodes, leading the electrodes onto the hard coat layer by printing a conductive paint on the hard coat layer in such a manner as to bury the holes with the paint, to thus form a wiring pattern on the hard coat layer, and mounting a driver IC on the hard coat layer; however, it has been found that such a method has a room to be improved.
On the other hand, in manufacture of a simple matrix type display in which luminescent pixels of an organic EL device are two-dimensionally arranged, a back surface side electrode layer must be processed into a stripe pattern. Further, in manufacture of a full-color display, a luminescent layer of an organic EL device must be processed into a pattern.
Since organic layers of an organic EL device are weak against a solvent, it is difficult to process them by lithography using a resist. Accordingly, each organic EL layer is processed into a pattern by vapor-deposition using a mask. Such vapor-deposition using the mask requires complicated steps. In this case, as the pattern becomes finer, the mask is made as close to the substrate as possible for reducing the degree of runabout of a material to be vapor-deposited on the back side of the mask.
If the mask is brought into contact with the substrate, however, it may damage and/or contaminate an already-formed organic EL layer. For this reason, it has been expected to interpose spacers each having a specific height between the substrate and the mask. With respect to these spacers, if the spacers interposed between the substrate and the mask are positioned not at an image area of the substrate but at the outer ends thereof, it is required to make the substrate and the mask as flat as possible, and particularly, if the mask is thin, it is required to provide a mechanism of imparting a tension to the mask.
An object of the present invention is to provide an optical device which is allowed to be connected to the adjacent one without a gap put therebetween and to be connected to parts to be mounted and which is improved to form a stacked body including organic layers without damaging the surface of an already-formed organic layer by a vapor-deposition mask, and to provide a method of manufacturing the optical device.
To achieve the above object, according to a first aspect of the present invention, there is provided an optical device including: electrodes arranged on a base; a stacked body provided on the electrodes in such a manner as to cover at least optical operation regions; an insulating layer formed in such a manner as to cover the top surface of the stacked body; and conductive projections provided on the electrodes in such a manner as to be located in non-optical operation regions; wherein the projections are buried in through-holes formed in the insulating layer in such a manner that the top surfaces of the projections are higher than the top surface of the stacked body and also nearly equal to or less than the top surface of the insulating layer; and exposed portions of the projections are electrically led onto the insulating layer.
The invention having the above configuration has the following advantages. Since the conductive projections provided on the electrodes in the non-optical operation regions are electrically led onto the insulating layer, a part (for example, electronic part) to be mounted on the insulating layer can be wired to the lead portions of the projections. Accordingly, the optical elements (for example, organic EL devices) can be flatly connected to each other without gaps put therebetween. Also, when the exposed portions of the projections are electrically led onto the insulating layer, a conductive layer can be formed in such a manner as to be desirably stuck on the exposed portions of the projections because the top surfaces of the projections buried in the through-holes formed in the insulating layer are equal to or less than the top surface of the insulating layer. This is effective to facilitate formation of wiring for the projections and hence to stabilize the mounting of the electronic part. Further, since the top surfaces of the projections are higher than the surface of the stacked body, the projections can function as spacers for vapor-deposition masks upon formation of the stacked body in the optical operation regions, so that it is possible to prevent from damaging the surface of an already-formed film by the mask.
According to a second aspect of the present invention, there is provided a method of manufacturing an optical device in which a stacked body is provided on electrodes arranged in a base in such a manner as to cover at least optical operation regions and the top surface of the stacked body is covered with an insulating layer, the method including the steps of: forming conductive projections on the electrodes in such a manner that the projections are located in non-optical operation regions and the top surfaces of the projections are higher than the top surface of the stacked body; and disposing a mask on the projections which are taken as spacers, and forming layers constituting the stacked body through the mask.
In accordance with the present invention, it is possible to manufacture the above-described optical device with a high reproductivity. Further, since the conductive projections are higher than the top surface of the stacked body, connection portions of wires connected to a part (for example, an electronic part) to be mounted are led out via the projections, so that it is possible to omit the step of forming through-holes for connection with the part to be mounted, and hence to improve the productivity.
In the above optical device and the method of the manufacturing the optical device according to the present invention, preferably, the projections are composed of metal bumps provided on the electrodes; a conductive layer is formed on the metal bumps in such a manner as to cover the metal bumps and is then processed into a conductive pattern. The metal bumps may be made from nickel paste, silver paste, or carbon paste.
The method of manufacturing an optical device, preferably, further includes the steps of: forming the electrodes on the base using a first mask having a specific pattern; forming the projections having a specific pattern in the non-optical operation regions on the electrodes by a physical vapor-deposition method or a plating method; and disposing a second mask having a specific pattern on the projections, and forming at least counter electrodes facing to the electrodes, among components of the stacked body by the physical vapor-deposition method.